JP3107701B2 - High hardness cemented carbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cemented carbide containing a large amount of hexagonal tungsten carbide having a developed (001) crystal plane. More specifically, the invention relates to a cutting tool, a drill, an end mill, a cutter and the like. Wear resistance such as cutting tools such as indexable inserts, insert tips, brazing tips, and solid tips, plastic working tools such as drawing, ironing and forging dies, and shearing tools such as punching dies and slitters. Bits used in tools, road works, civil works, and tunnel works, civil mining tools such as drilling tools, mechanical seals, sliding materials such as bearings, clock frames, fishing gear, tie pins, and nozzles. High-hardness cemented carbide suitable for decorative and corrosion-resistant materials, and various structural materials used in machine parts and chemical industry parts Than it is.

[0002]

2. Description of the Related Art Cemented carbides include hexagonal tungsten carbide,
Or, it is a sintered alloy in which a hard phase composed of hexagonal tungsten carbide and a cubic compound is combined with a binder phase containing Co and / or Ni as a main component. It is widely used for applications. This cemented carbide is mainly made of hexagonal tungsten carbide,
The properties can be adjusted by the content of the binder phase and the content of the cubic compound. However, in general, the properties of cemented carbide are such that when hardness and wear resistance are increased, strength, toughness and fracture resistance are reduced, and when strength, toughness and fracture resistance are increased, hardness and wear resistance are reduced. There is a problem of showing a trade-off tendency to decrease.

[0003] In order to solve this problem, as a proposal from one direction, attention has been paid to the anisotropy of mechanical properties due to the crystal plane of hexagonal tungsten carbide. Since the (001) crystal plane of the crystalline tungsten carbide has the highest hardness and the (100) crystal plane has the highest elastic modulus, the tungsten carbide containing a (001) crystal plane with a high hardness or a crystal plane grown on the tungsten carbide is included. There is a cemented carbide or a method for producing the same.

[0004] A representative example of the prior art relating to a tungsten carbide-containing cemented carbide with a crystal face grown is disclosed in
JP-A-7-23049, JP-B-47-23050, JP-A-57-34008, JP-A-2-472.
39, JP-A-2-51408, JP-A-2-51
138434, JP-A-2-274827 and JP-A-5-339659.

[0005]

Among the prior art related to tungsten carbide containing cemented carbides with crystal faces grown,
JP-B-47-23049, JP-B-47-2305
No. 0, JP-A-2-274827 and JP-A-5-339659 disclose a cemented carbide in which the crystal plane is not clear but a certain crystal plane of tungsten carbide is grown or a method for producing the same. Are listed. The cemented carbide described in these four publications or the cemented carbide obtained by the described manufacturing method has a low growth rate of the (001) crystal plane of tungsten carbide or the (001) crystal plane. Hardness, wear resistance, strength, toughness,
There is a problem that the effect of improving various properties of a cemented carbide represented by fracture resistance is weak, and in particular, it is not possible to improve all of these properties.

Japanese Patent Application Laid-Open No. 57-34008 describes a method for producing twin tungsten carbide grown on a (001) crystal plane and joined on a (001) plane. Twin tungsten carbide described in the same publication is difficult to produce, and the production rate is low, so even if a cemented carbide is produced using this, the same as the cemented carbide described in the above publication However, there is a problem that the effect is weak.

Further, JP-A-2-47239, JP-A-2-51408 and JP-A-2-13843.
No. 4 describes a cemented carbide containing tungsten carbide having a (0001) crystal plane grown thereon, or a composition for obtaining the cemented carbide. The cemented carbide obtained from these three publications or the cemented carbide obtained from the composition thereof has a low content of tungsten carbide which has grown the (001) crystal plane. As with the cemented carbides described, there is the problem that their effects are weak.

The present invention has solved the above-mentioned problems. More specifically, the present invention relates to a hexagonal tungsten carbide (00
1) A cemented carbide with a high crystal plane growth ratio and a high content is used. It has high hardness, excellent wear resistance and high strength.
It is an object of the present invention to provide a high-hardness cemented carbide having high toughness and excellent fracture resistance, and exhibiting a synergistic effect of these characteristics to achieve a long life.

[0009]

Means for Solving the Problems The inventors of the present invention have, for many years, made it possible to reduce the strength and wear resistance of a cemented carbide without reducing its hardness and wear resistance.
Investigations to improve toughness and fracture resistance were carried out. The peak strength of the (001) crystal plane of hexagonal tungsten carbide in the X-ray diffraction curve obtained from an arbitrary cross section of the cemented carbide and various properties of the cemented carbide were examined. That there is a correlation with the characteristics,
ASTM card (AMERICA SOCIETY
Hexagonal tungsten carbide (W) by Cu X-ray diffraction curve in FOR TESTING MATERIALS
The (001) crystal plane strength ratio of (C) to the (101) crystal plane strength is described as 0.45, and the hexagonal crystal is obtained by a Cu X-ray diffraction curve at an arbitrary cross section of a conventional cemented carbide actually used in practice. The ratio of the (001) crystal plane strength to the (101) crystal plane strength of the tungsten carbide is 0.25 to 0.45, whereas the (10) crystal plane strength of the hexagonal tungsten carbide is (10).
1) It has been found that increasing the (001) crystal plane strength ratio with respect to the crystal plane strength results in a cemented carbide having improved hardness, wear resistance, toughness, strength and fracture resistance. It has been completed.

[0010] That is, the high-hardness cemented carbide of the present invention comprises C
o, Ni, Co-Ni alloy, Co-Cr alloy, Ni-C
In a cemented carbide consisting of 3 to 40% by volume of a binder phase of an r alloy, a Co—Ni—Cr alloy, a Ni—Mo alloy, or a Co—W alloy, and the balance being hexagonal tungsten carbide and unavoidable impurities, When the peak intensity of the (101) crystal plane in the X-ray diffraction curve of tungsten by Cu-Kα ray is expressed as h (101), and the peak intensity of the (001) crystal plane is expressed as h (001), h (001) / H
(101) ≧ 0.50.

The binder phase in the cemented carbide of the present invention is, for example, Co, Ni, Co—Ni alloy, Co—C
r alloy, Ni-Cr alloy, Co-Ni-Cr alloy, Ni
-Mo alloy, Co-W alloy, or an alloy containing a small amount of an element constituting the cubic compound described later, mainly Fe as an inevitable impurity, or the like. Of these binder phases, for applications in which corrosion resistance is emphasized, Ni-Cr alloys, Co-Cr alloys, Ni-Co-C containing 2 to 20% by volume of Cr with respect to the total binder phase amount are used.
An r alloy is preferred, and for applications where emphasis is placed on wear resistance, a Co-W alloy, a Ni-W alloy, a Co-Ni- alloy containing 0.5 to 5% by volume of W with respect to the total binder phase amount. W alloys are preferred. If the amount of the binder phase is less than 3% by volume with respect to the entire cemented carbide, sintering becomes difficult and pits are apt to remain inside. As a result, the strength and hardness are significantly reduced, and conversely, 40%. When the content exceeds% by volume, the amount of hexagonal tungsten carbide relatively decreases, and as a result, the hardness and the wear resistance are significantly reduced.

The hexagonal tungsten carbide bonded by the bonded phase corresponds to WC described in ASTM card 25-1047, but unlike WC described in this ASTM card, it is based on Cu-Kα radiation. The peak intensity of the (101) crystal plane in the X-ray diffraction curve is represented by h (101)
Where the peak intensity of the (001) crystal plane is h (00
When expressed as 1), h (001) / h (101) ≧
0.50, preferably h (001) / h (1
01) ≧ 0.50, particularly preferably h (001) / h
(101) ≧ 0.60. This h (0
01) / h (101) is less than 0.50, W (001) crystal planes are grown in hexagonal tungsten carbide.
C decreases, or the growth rate of the (001) crystal plane decreases, and the effect of improving the hardness, wear resistance, toughness, strength and fracture resistance of the alloy decreases.

As inevitable impurities, there are impurities that are mixed in commercially available starting materials used in the manufacturing method described later and impurities that are mixed in the manufacturing process, particularly, the process of mixing and grinding the starting materials. Examples of inevitable impurities include Fe, Al, and oxygen.

The cemented carbide of the present invention comprising the above-mentioned binder phase, hexagonal tungsten carbide and unavoidable impurities, when it does not reach a high temperature at normal temperature or at the time of use, specifically, for example, the above-mentioned wear-resistant tool, civil engineering Highly effective as a mine tool, sliding material, decoration, corrosion-resistant material or structural material,
In applications where the temperature rises to a high temperature during use, specifically, for example, cutting tools, particularly P-series cemented carbide as cutting tools, and JIS standard steel cutting, M as general-purpose cutting used for both steel and castings Consideration of hardness at high temperature, abrasion resistance, thermal shock resistance, toughness, strength, welding resistance, peeling resistance, etc. for some series cemented carbide and K series cemented carbide used for casting The following cemented carbides of the present invention are preferred.

That is, the high-hardness cemented carbide according to the present invention comprises C
o, Ni, Co-Ni alloy, Co-Cr alloy, Ni-C
3 to 40% by volume of a binder phase of an r alloy, a Co—Ni—Cr alloy, a Ni—Mo alloy, or a Co—W alloy;
at least one cubic compound of carbides, nitrides and mutual solid solutions of metals of groups a, 5a and 6a;
In a cemented carbide composed of 5% by volume or less and a balance of hexagonal tungsten carbide and unavoidable impurities, the peak intensity of the (101) crystal plane in the X-ray diffraction curve of the hexagonal tungsten carbide by the Cu-Kα ray is represented by h ( When the peak intensity of the (001) crystal plane is expressed as h (001), h (001) / h (101) ≧ 0.50.

The cubic compound in the cemented carbide according to the present invention is specifically, for example, TiC, ZrC, HfC,
VC, NbC, TaC, V ₄ C ₃ , Mo ₂ C, Cr ₃ C ₂ ,
TiN, ZrN, Ti (C, N), (W, Ti) C,
(W, Ti, Ta) C, (W, Ti) (C, N),
(W, Ti, Ta) (C, N), (W, Nb, Zr)
(C, N), (W, Ti, Nb, Ta) C, (W, T
i, Nb, Ta) (C, N). When the amount of the cubic compound exceeds 55% by volume,
Because the amount of hexagonal tungsten carbide relatively decreases,
The effect of improving hardness, strength and toughness decreases.

Further, a cemented carbide of the present invention is used as a base material, and carbides of metals belonging to groups 4a, 5a and 6a of the periodic table are formed on the base material.
Nitride, carbonate, nitride, Al nitride, oxide,
Abrasion resistance is further improved by coating a hard coating of at least one single layer or two or more layers of Si carbide, nitride, diamond, diamond-like carbon, cubic boron nitride, and hard boron nitride. However, it is preferable because a longer life can be expected in addition to the high toughness and high strength of the base material itself.

The cemented carbide of the present invention is disclosed in, for example,
It is also conceivable to manufacture by separating and extracting twin tungsten carbide described in JP-A-34008 and using it as a starting material.
composite carbide powder comprising at least one of i and Cr, or W
1 of a mixture comprising ₂ C and at least one of Co, Ni and Cr
It is particularly preferable that the post-process is carried out by a conventional powder metallurgy method, and that it can be easily and stably prepared by using either or both as a starting material. This will be specifically described in Examples.

[0019]

According to the high hardness cemented carbide of the present invention, the (001) crystal plane of hexagonal tungsten carbide is
(101) It is relatively increased with respect to the crystal plane, and as a result, contributes to the effect of improving the hardness in an arbitrary cross section and the effect of improving the strength and toughness of the entire alloy.

[0020]

EXAMPLES First, using commercially available W having an average particle size of 0.5 μm, carbon black having an average particle size of 0.02 μm (denoted as C in the table), and Co having an average particle size of 1 μm, _The blended and mixed powders having a composition to produce ₂ C, Co ₂ W ₄ C and Co ₃ W ₃ C are inserted into a carbon boat and fired at 1400 ° C. for 1 hour in a vacuum furnace at an atmospheric pressure of 10 ⁻² Torr. , W ₂ C, Co ₂ W ₄ C, and Co ₃ W ₃ C powders were obtained.

The thus obtained W ₂ C, Co ₂ W ₄ C, Co ₃ W
₃ C, the above-mentioned W, Co, and carbon black, and commercially available WC having an average particle size of 2.0 μm, and an average particle size of 1 to 2 μm.
m Cr ₃ C ₂ , Ni, (W, Ti, Ta) C (weight ratio WC / TiC / TaC = 50/20/30, WTT in the table)
), Each powder was weighed to the composition shown in Table 1, inserted into a stainless steel pot together with an acetone solvent and a cemented carbide ball, mixed and pulverized for 48 hours, and then dried to obtain a mixed powder. Was. A mold is filled with these mixed powders and 2t
A green compact of about 5.5 x 9.5 x 29 mm was prepared by applying a pressure of / cm ² , placed on a sheet made of alumina and carbon fiber, and placed in a vacuum at an atmospheric pressure of 10 ^-2 Torr. By heating and holding at the temperature described in 1 for 1 hour, cemented carbides of inventive products 1 to 9 and comparative products 1 to 10 were obtained.

The thus-obtained cemented carbides of the present invention products 1 to 9 and comparative products 1 to 10 were wet-ground with a # 230 diamond grindstone to form a 4.0 × 8.0 × 25.0 mm shape. The bending force was measured by the JIS method, and the results are shown in Table 2. After one surface of the same sample was lapped with a 1 μm diamond paste, Vickers hardness (load: 20 kgf) was measured. The results are shown in Table 2.
Furthermore, a photograph of the structure of the lapping surface of each sample is taken with an electron microscope, and the volume ratio of the binder phase, cubic compound, hexagonal tungsten carbide (WC) and the average particle size of WC are measured with an image processing device. Table 1 shows the former and Table 2 shows the latter
It was also described in. Next, for each sample, the peak intensity of the (001) crystal plane and the (101) crystal plane of hexagonal tungsten carbide was measured by X-ray diffraction using a Cu target and a Ni filter, and the peak intensity ratio h (00)
1) / h (101) was calculated, and the results are shown in Table 2.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

The high-hardness cemented carbide of the present invention has a hardness of about 1.1 to 2.9 (GPa) as compared with a conventional cemented carbide having the same composition and the same WC grain size. ) The same composition and the same WC, which cannot be achieved by the conventional cemented carbide, which is high and the bending strength is increased by about 0.1 to 0.4 (GPa).
There is an excellent effect that both hardness and strength can be increased under the condition of particle size.

Claims (2)

(57) [Claims] 1. Co, Ni, Co-Ni binary alloy, Co
-Cr binary alloy, Ni-Cr binary alloy, Co-Ni
-Cr ternary alloy, Ni-Mo binary alloy or Co-
In a cemented carbide consisting of 3 to 40% by volume of a binder phase of a W binary alloy and the remainder consisting of hexagonal tungsten carbide and unavoidable impurities, (101) in the X-ray diffraction curve of the hexagonal tungsten carbide by Cu-Kα ray When the peak intensity of the crystal plane is represented by h (101) and the peak intensity of the (001) crystal plane is represented by h (001), h (001) / h
(101) A high-hardness cemented carbide characterized by being ≧ 0.50. 2. Co, Ni, Co—Ni binary alloy, Co
-Cr binary alloy, Ni-Cr binary alloy, Co-Ni
-Cr ternary alloy, Ni-Mo binary alloy or Co-
3 to 40% by volume of the binder phase of the W binary alloy and 4 of the periodic table
at least one cubic compound of carbides, nitrides and mutual solid solutions of metals of groups a, 5a and 6a;
In a cemented carbide composed of 5% by volume or less and a balance of hexagonal tungsten carbide and unavoidable impurities, the peak intensity of the (101) crystal plane in the X-ray diffraction curve of the hexagonal tungsten carbide by the Cu-Kα ray is represented by h ( 101), and h (001) / h (101) ≧ 0.50 when the peak intensity of the (001) crystal plane is represented by h (001).